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Full text of "IS 8733: Tolerances for single start gear hobs"

**************** 



*■ fe^K 




Disclosure to Promote the Right To Information 

Whereas the Parliament of India has set out to provide a practical regime of right to 
information for citizens to secure access to information under the control of public authorities, 
in order to promote transparency and accountability in the working of every public authority, 
and whereas the attached publication of the Bureau of Indian Standards is of particular interest 
to the public, particularly disadvantaged communities and those engaged in the pursuit of 
education and knowledge, the attached public safety standard is made available to promote the 
timely dissemination of this information in an accurate manner to the public. 




Mazdoor Kisan Shakti Sangathan 
"The Right to Information, The Right to Live" 



IS 8733 (1978) : Tolerances for single start gear hobs [PGD 
32: Cutting tools] 




Jawaharlal Nehru 
'Step Out From the Old to the New' 



■K^y / 1 juaaaws^fea rs^^TTF^ 



2*S< W I *>S*V2^NK^ 



^frcvvv^ 



Satyanarayan Gangaram Pitroda 
Invent a New India Using Knowledge 



Bhartrhari — Nitisatakam 
"Knowledge is such a treasure which cannot be stolen" 




.^^_ 



• 




BLANK PAGE 



*rt*2V^ 





PROTECTED BY COPYRIGHT 



UDC 62V914-6 : 621*833 : 621*753*1 IS : 8733 - 1 978 




( Reaffirmed 2002 ) 
Indian Standard 

TOLERANCES FOR 
SINGLE START GEAR HOBS 



o 

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O 
Q 

Ui 

0? 
<D 

1 

E 
o 
O 

*5 

c 
o 



1. Scope— Covers the tolerances for single start gear hobs, suitable for modules 1 to 20, conform- 
ing to fS : 2535-1978 ' Basic rack and modules of cylindrical gears for general engineering and heavy 
engineering (second revision )\ The tolerances specified in the standard apply to all pressure 
angles. 



2. Grades 

2.1 Gear hobs shall be classified into the following grades of accuracy: 

Grade AA High precision ground hobs 

Grade A Precision ground hobs 

Grade B Commercial ground hobs 

Grade C Precision unground hobs 

Grade D Commercial unground hobs 

2.2 Bearing surface length of bore for all grades shall be 66 percent except for Grade AA. 



EXPLANATORY NOTE 



In the preparation of this standard considerable assistance has been derived from DIN 3968- 
1960 'Toleranzen eingangiger Walzfraser fur Stirnrader mit Evolventenverzahnung (Tolerances for 
single-start hobs for involute spur gears ) ' issued by Deutsches Institut fur Normung. 



Adopted 23 February 1978 



© August 1978, IS! 



INDIAN STANDARDS INSTITUTION 

MANAK BHAVAN, 9 BAHADUR SHAH ZAFAR MARG 

NEW DELHI 110002 



3. Tolerances 















All tolerances in micrometres ( 1 m 


crometre = 


= 0*001 mm 


). 












SI 
No. 


Element 

to be 
Checked 


Illustration 


Symbol 

for 

Tolerance 


Grade 


Module 


For 

1 


Over 

1 
Up to 

1"6 


Over 
1-6 

Up to 
2-5 


Over 
2'5 

Up to 
4 


Over 

4 

Up to 

6'3 


Over 

6"3 
Up to 

10 


Over 

10 
Up to 

16 


Over 

16 
Up to 

20 


1 


Tolerance on 
bore diameter 
(d)* 


i 


r\ r\ f\ r\ f\ 




— 9 


AA 
A 
B 
C 
D 


H5t 
H5f 
H6f 
H6t 
K7t 


J \J \J \J XJ \ 


J 


v/////////y//A 










-4>|d 


p 








/////777T/////A 




|A AAA Al 




1/ \J \J \J \J \J 


2 


Form 
tolerance 
of bore* 


— 


— 


All 

grades 


One half the bore tolerance 


3 


Interchange- 
able tole- 
rance for 
keyway 


— 


— 


All 
grades 


According to IS : 6285-1971 ' Dimensions for interchangeabiiity of mining 
and milling arbors with key drive ' 


3 cutters 


4 


Radial 

runout of hub 
diameter with 
respect to 
bore axis 








ftp 


AA 


5 


5 


5 


5 


5 


5 


6 


6 




J \J \J \J \J \ 


A 


5 


5 


5 


6 


8 


10 


12 


16 




y///< 


////^ 


W//A 


T- 


/ / y> / y 






B 


6 


6 


6 


8 


10 


12 


16 
25 


20 




. . . 


-<s//////""'"\ 


C 


10 


10 


10 






20 


32 


♦ 


WVV\Al 


^ 


12 | 


16 


. 






D 


Not defined 







*Bores with recess are to be treated as a single-diameter through bore with regard to diameter and form tolerances. For hobs of Grade AA, it is desirable that the bore should not be 
made with a recess, 

tAccording to IS : 919-1963 ' Recommendations for limits and fits for engineering ( revised ) \ 



(Continued) 



All tolerances in micrometres ( 1 micrometre = 0*001 mm ). 



f 

SI 
No. 


Element 

to be 
Checked 




Illustration 




Symbol 

for 

Tolerance 


Grade 


Module 






For 
1 


Over 

1 
Up to 

V6 


Over 

1'6 
Up to 

25 


Over 

2-5 
Up to 

4 


Over 

4 
Up to 

63 


Over 
63 

Up to 
10 


Over 

10 
Up to 

16 


Over 

16 
Up to 

20 




5 


Axial runout 
of hub on 
both faces 
with respect 
to bore axis 




ft> 


AA 


3 


3 


3 


3 


3 


4 


5 


5 










A 


3 


3 


3 


5 


5 


8 


8 


10 






J \J \J \J \J \ 




k> 


ZZtZZ/ssff 


Y/f// 


K> 


B 


4 


4 


4 


6 


6 


10 


10 


12 








\//// //////////. 


C 


6 


6 


6 


10 


10 


16 


16 


20 






\r\ r 


\n AAl 








\J \J \J \J 






D 


10 


10 


12 


16 


16 


25 


25 


32 




Radial 
runoiit on 
tooth tips 
with respect 
to bore 
axis 




frk 


AA 


10 


10 


12 


16 


20 


25 


32 


40 








f\^K^Pd\ 




A 


12 


16 


20 


25 


32 


40 


50 


63 








V/////////////A 


















B 


25 


32 


40 


50 


63 


80 


100 


125 




6 










Y////////////A x 








\{*J\f\f 


u i 




C 


50 


63 


80 


100 


125 


160 


200 


250 


5> 










i 




D 


100 


125 


160 


200 


250 


315 


400 


500 


00 
-J 
CO 
CO 
































{Continued) 


*-4 



Alf tolerances in micrometres ( 1 micrometre = 0'001 mm ). 



SI 
No. 



Element 

to be 
Checked 



Form and 
positional 
tolerance of 
cutting 
faces 



Illustration 



PLANE OF AXIS 



- ^.CUTTING 

/ 'depth 




DISTANCE U IS THE AMOUNT 
BY WHICH DESIGN LINE 
IS DISTANT FROM PLANE 
OF HOB AXIS 
(ZERO WHEN RAKE ANGLE IS 0°) 




TOOTH TIP! 

TEST DIAGRAM 



Symbol 

for 

Tolerance 



FtN 



Grade 



AA 



For 
1 



10 



12 



25 



50 



100 



Over 

1 

Up to 

1-6 



10 



16 



32 



63 



125 



Module 



Over 
1-6 

Up to 
2-5 



12 



20 



40 



80 



160 



Over 

2-5 

Up to 

4 



16 



25 



50 



100 



200 



Over 

4 
up to 

6'3 



20 



32 



63 



125 



250 



Over 

6-3 

Up to 

10 



25 



40 



160 



315 



Over 

10 
Up to 

16 



32 



50 



100 



200 



400 



Over 

16 
Up to 

20 



40 



63 



125 



250 



500 



{Continued) 



AH tolerances in micrometres ( 1 micrometre « 0*001 mm ). 



SI 
No. 



Element 

to be 
Cheeked 



Tolerance on 
tooth spacing 
at the 
middle of 
the tooth 
height 



Maximum 
tooth spacing 
error bet- 
ween two 
adjacent 
teeth 



Illustration 














,1 




















t 
ft 


N 






♦ 

ftr 

t 


i 




















1 





ZERO 



1 234 5678910 1112 
TEST DIAGRAM 







1 




























I 

tl 


1 






















i 









ZERO 



1 2 3 4 5 6 7 8 9 10 11 12 



Symbol 

for 

Tolerance 



f\N* 



f»Nt 



Grade 



AA 



AA 



VtN is the difference between the actual value and designed value of the gash spacing. 
tTooth spacing error /uN is the actual difference in the spacing of two adjacent gashes. 



Module 



For 

1 



±10 



±12 



±25 



±50 



±100 



10 



12 



25 



50 



100 



Over 

1 
Up to 

1-6 



±10 



±16 



±53 



±125 



10 



16 



63 



125 



Over 
1-6 

Up to 
2'5 



±12 



±20 



±40 



±160 



12 



20 



40 



80 



160 



Over 

2'5 

Up to 

4 



±16 



±25 



±50 



±100 



Over 

4 
Up to 

6-3 



±20 



±32 



±63 



±125 



±200 



16. 



25 



50 



100 



200 



±250 



20 



32 



63 



125 



250 



Over 
6'3 

Up to 
10 



±25 



±40 



±80 



±160 



±315 



25 



40 



80 



160 



315 



Over 

10 
Up to 

16 



±32 



±50 



±100 



±200 



±400 



32 



50 



100 



200 



400 



Over 

16 
Up to 

20 



±40 



±63 



±125 



±250 



±500 



40 



63 



125 



250 



500 



( Continued ) 



ih 



■*4 

t 



SI 
No. 



10 



Element 

to be 
Checked 



11 



Maximum 
cumulative 
tooth spac- 
ing error 
measured 
at half tooth 
height 



Lead error 
of gash over 
100 mm hob 
length 



All tolerances In micrometres ( 1 micrometre = 0*001 mm ). 



Illustration 






/ 


/ 
























s 


s 


^ 




L 










>— 


Fiw 


< 


y 










r 


s 


>-* 


s 


U 


h 


- ' iN 











1 2 3 4 5 6 7 8 9 10 1112 

TEST DIAGRAM 




Symbol 

for 

Tolerance 



FtN* 



/hn 



Grade 



AA 



AA 



For 
1 



20 



25 



50 



100 



200 



Modulo 



Over 

1 
Up to 

1'6 



20 



63 



125 



250 



Over 
1*6 

Up to 
2-5 



25 



40 



80 



160 



315 400 



Ovef 

25 

Up to 

4 



32 



50 



100 



Over 

4 
Up to 

6*3 



40 



63 



125 



200 



250 



500 



Over 

6'3 

Up to 

10 



50 



80 



160 



315 



630 



± 50 



± 70 



±100 



±140 



±200 



•The tolerance FtH is referred to the total pitch error, that is to say that the largest cumulative pitch error measured on the hob tested. 



Over 

10 
Up to 

16 



63 



100 



200 



400 



800 



Over 

16 
Up to 

20 



80 



125 



2S0 



500 



1000 



(Continued ) 



CO 



CO 
CO 
I 

CP 

-J 

00 















All tolerances in micrometres ( 1 micrometre *= 


= 0'001 mm 


)■ 












SI 
No. 


Element 

to be 
Checked 


Illustration 


Symbol 

for 
Tolerance 


Grade 


Module 


For* 

1 


Over 

1 
Up to 

1*6 


Over 
1-6 

Up to 
2'5 


Over 

25 
Up to 

4 


Over 

4 
Up to 

6'3 


Over 
63 

Up to 
10 


Over 

10 
Up to 

16 


Over 
16 

Up to 
20 


12 
13 


Permissible 
error over 
the straight 
flank from 
the design 
form 


A% 


FfS 


AA 


6 


6 


6 


8 


10 


12 


14 


18 


A 


10 


11 


12 


14 


16 


20 


25 


32 


B 


20 


22 


25 


28 


32 


40 


50 


63 


C 


40 


45 


50 


56 


63 


80 


100 


125 


D 


Not defined 


Tolerance on 
tooth thick- 
ness on the 
pitch 
cylinder 




— s— - 




U 


AA 


-16 


-16 


-16 


-20 


-25 


-32 


-40 


-50 


/t 


\ 


A 


-25 


-28 


-32 


-36 


-40 


-50 


-63 


-80 




—a 


B 


-50 


-56 


-63 


-71 


-80 


-100 


-125 


-160 
-320 


/ 


V 


C 


-100 


-112 


-125 


-140 


-160 


-200 


-250 




D 


-100 


-112 


-125 


-140 


-160 


-200 


-250 


-320 

±12 


14 


Hob lead 
from cutting 
edge to cutt- 
ing edge in 
the direction 
of hand 




H|sj»H 


-f H P U L. 


/hf 


AA 


±4 


±4 


±4 


±5 


±6 


±8 


±10 


J 


i(H N t 


H) _ 


i(H N iH) HF 

I 


hm 


A 


±6 


±7 


±8 


±9 


±10 


±12 


±16 


±20 


Ji \IJ \. 

where 

Hn = lead of gashes, 

H = hob Tead ( helix ) f and 

/ = number of gashes or tooth rows. 

The sian in the oarentheses is dIus r -4— ^ if 


B 


±12 


±14 


±16 


±18 


±20 


±25 


±32 


±40 


C 


±25 


±28 


±32 


±36 


±40 


±50 


±63 


±80 


gash 
direc 
same 


lead and the 
tion, and ne 
1 direction 


hob le 
gative 


ad are in the opposite 
[ — ) if they are in the 


D 


±50 


±56 


±63 


±71 


±80 


±100 


±125 ±160 



CO 



CO 
CO 



(Continued) 











All tolerances in micrometres ( 1- micrometre = 


= 0001 mm 


>. 












SI 
No. 


Element 
to be 

Checked 


Illustration 


Symbol 

for 

Tolerance 


Grade 


Module 


For 
1 


Over 

1 
Up to 

V6 


Over 

1-6 
Up to 

2'5 


Over 

2-5 

Up to 

4 


Over 

4 

Up to 

6*3 


Over 

6'3 

Up to 

10 


Over 

10 
Up to 

16 


Over 

16 
Up to 

20 


15 


Hob lead in 
the direction 
of hand 
between any 
two cutting 
edges on the 
same thread 


n.H^.H c 


■ 




fH* 


AA 


6 


6 


6 


8 


10 


12 


14 


18 


i(H N ±H)~ nr 

/ ' / / A\\X\ / / ' 




A 


10 


11 


12 


14 


16 


20 


25 


32 


•^-ij ^kl' ""WJ 

where 

Wn — Lead of gashes, 

H = hob lead ( helix ), 

/ = number of gashes or tooth rows, and 

n «= number of cutting edges on which the 

measurement is made. 
The sign in the parentheses is plus ( 4- ) if 
gash lead and the hob lead are in the opposite 
direction, and negative ( — ) if they are in the 
same direction 


B 


20 


22 


25 


28 


32 


40 


50 


63 


C 


40 


45 


50 


56 


63 


80 


100 


125 


D 


80 


90 


100 


112 


125 


160 


200 


250 


16 


Individual 
base pitch 
error 


te_ f 


fe 


AA 


±4 


±4 


±4 


±5 


±6 


±8 


±10 


±12 


// \\ // \dl 




A 


±6 


±7 


±8 


±9 


±10 


±12 


±16 


±20 


i» \\ J^^ \\ /' 




B 


±12 


±14 


±16 


±18 


±20 


±25 


±32 


±40 


where 

U — base pitch, ahd 


C 


±25 


±28 


±32 


±36 


±40 


±50 


±63 


±80 


/ = number of gashes 









Not defined 



(Continued) 



18 



SI 


Element 


No. 


to be 




Checked 




Cumulative 




base pitch 


17 


error within 




the contact 




region 



Diameter 
tolerance 
over hob 
length 



All tolerances in micrometres ( 1 micrometre = 0'001 mm ). 



Illustration 





^CONTACT, 
REGION 

TEST DIAGRAM 



Symbol 

for 

Tolerance 



Grade 



AA 



AA 



For 
1 



12 



25 



50 



40 



20 



40 



Module 



Over 

1 

Up to 

V6 



14 



28 



56 



12 



25 



50 



Over 

re 

Up to 
25 



16 



32 



63 



Over 

2'5 

Up to 

4 



10 



16 



32 



63 



10 



18 



36 



7! 



Over 

4 

Up to 

6-3 



12 



20 



40 



Over 
6'3 

Up to 
10 



16 



25 



50 



80 



100 



Not defined 



12 



20 



40 



80 



16 



25 



50 



100 



20 



32 



63 



125 



Not defined 



Over 

10 
Up to 

16 



20 



32 



63 



125 



25 



40 



80 



160 



Over 

16 
Up to 

20 



25 



40 



80 



160 



32 



50 



100 



200